Closed mitral commissurotomy (CMC) was performed on 232 patients (67M, 165F) with isolated mitral valve disease from 1954-1980. Mean age was 41 yrs. and operative mortality was 4%. Pre- and postop catheterization was obtained in 70% of patients. Mean NYHA Functional Class preop was 2.7 and improved to 1.6 after CMC. Mean mitral valve gradient (MG) decreased from 15 to 6(p.001). FC was 1.6 and 1.8 at 5 and 10 yrs after CMC; 20 patients (10%) underwent more than one CMC. Actuarial survival free of mitral valve replacement (MVR) was 83 and 66 at 5 and 10 years. MVR was required in 42 patients (15M, 27F) a mean of 9 years after CMC (range 1-26 yrs). In this subgroup the CMC initially improved FC from 2.7 to 1.9 and MG from 13 to (p.001). Patients subsequently undergoing MVR had a higher mean LA pressure after CMC mortality for MVR was 12%. MVR improved FC from 3.1 to 1.7 and MG from 12 to 5(p.001). At both 5 and 10 years after MVR FC was 2.0. CMC provides useful palliation even in 20% of patients who ultimately require MVR.